1. Field of the Invention
This invention relates to be field of inertial guidance and more particularly to the field of ring laser gyroscopes and to the field of detector systems used by ring laser gyroscopes to detect rotational information from counterpropagating light beams.
2. Description of Prior Art
Detector systems used in ring laser gyroscope applications typically employ at least one partially transmissive mirror at locations in a resonant cavity through which components of a CW and a CCW beam are extracted. The beams are then combined using combining optics such as a prism. The combined beams are then directed onto a focal plane to form an illuminated spot in which interference patterns are characterized as areas of high and low intensity. As an ring laser gyroscope experiences an input body rate, the interference patterns move across the illuminated spot in response to the SAGNAC effect. Conventional ring laser gyroscope detector systems position an array of two or three PIN diode detectors in the illuminated spot on the focal plane, the diode detectors being positioned and biased to sense and provide electrical signals in response to movement of the interference pattern across their surface. The electrical signals thus provided are amplified and conditioned to provide digital body rate information.
A conventional ring laser gyroscope detector system will typically have an illuminated spot size of greater than 0.030 inches and will use diodes of 0.030 inches on an edge, and separated by 0.005 inches.
The diodes used are typically semiconductor or rectangular in shape. The size of the diode, the depth of the diffusion, the peak intensity of the illuminated spot and the separation of the interference patterns each combine to influence the detector system's signal to noise ratios and bandwidth.